FOXBOROUGH — The Patriots defense is always dealing with shadows. They’re in the shadow of their prolific offense and its canonized quarterback. They were overshadowed by J.J. Watt and the Houston Texans demolition crew of a defense entering Monday night’s matchup. Earlier in the season, it appeared the Patriots defense couldn’t cover their own shadow, especially if it ran a deep route.

What came to light Monday night in the Patriots’ 42-14 victory over the Texans in a game that was more beatdown than showdown for AFC supremacy is that the Patriots’ defensive improvement is not a figment of fertile imaginations, like thinking someone is behind you when it’s just your shadow. It’s real.

The Texans found that out the hard way, as they stared at the empty integer next to their name on the scoreboard for more than 38 minutes.

This wasn’t a dominant defensive performance against a callow rookie quarterback (Indianapolis), or an inept offense that has a QB better at finding the back of his right guard than an open receiver (New York Jets), or an offense more conservative than Ann Coulter (Dolphins). This was a defensive declarative sentence against the No. 2 scoring offense in the league, a unit that has a future Hall of Fame wide receiver in Andre Johnson and the NFL leader in touchdowns in running back Arian Foster.

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Texans quarterback Matt Schaub was not another quotidian QB for the Patriots to pile up turnovers against. Schaub had led Houston to wins in 15 of his last 16 starts and thrown for 3,944 yards and 26 touchdowns during that span. He’s not ordinary. The Patriots defense just made him look that way.

The NFL has done everything in its power to disabuse fans of the notion that defense is a valued and important part of the game. Being an NFL defender now is sort of like being a farmer in the Dust Bowl during the 1930s. It’s all famine and no feast. But defense does still matter if you have visions of hoisting the Lombardi Trophy.

Stats are for losers. Defense is for winners, and it appears the Patriots might have one worthy of January and February football after all.

New England’s much-maligned defense held Houston to just 42 yards rushing in the first half on 13 carries and 100 yards on 27 carries for the game. The Texans were 2 for 10 on third down after three quarters and finished 4 of 14.

The Patriots defense played like a unit with something to prove — that its players are not to be hidden in the dark, or covered up like an undesirable piece of furniture. Linebacker Jerod Mayo admitted the talk about the Texans was fuel for the defense.

“We feel like we just got to keep improving,” said safety Devin McCourty, who intercepted Schaub in the end zone in the first quarter. “Everyone says what they’re going to say. We know that we’re a good defense here. We know we’ve played really well the last couple of weeks. The biggest focus is just trying to build on that.”

The turning point in the game was McCourty’s interception. With the Patriots leading, 7-0, Houston drove to the New England 23. Schaub tried to throw a pass to Kevin Walter in the end zone. McCourty undercut the throw and picked it off in the end zone, returning it to the 18.

It was the Patriots’ 34th turnover of the year.

Six plays later, Brady found Brandon Lloyd for a 37-yard touchdown.

We know the Patriots can force turnovers and prey on miscues, but what made this performance the most impressive all year on the Other Side of the Ball was the caliber of competition and the fact that the Patriots only forced one turnover and still stifled the Texans’ attack.

“He’s a big man. He’s huge man. There was a play where I pulled around, and he’s huge,” said Texans left tackle Duane Brown. “He’s a great player. He has been a great player for a long time. Just a big man.”

Trailing, 21-0, the Texans went for it on fourth down twice in the first half in Patriots territory. The first time Walter dropped a would-be catch. The second time Schaub was pressured into a throw to nowhere because of heat from Mayo.

The only downside for the Patriots’ defense was the depletion of their defensive backs. They lost cornerback Aqib Talib, who shadowed Johnson. Talib hurt his hip late in the second quarter when he made a diving pass breakup of a ball intended for Johnson. Cornerback Alfonzo Dennard left the game with a hamstring injury in the second half.

Talib looks like the best in-season pick up in these parts since Orlando Cabrera took over at shortstop for the Red Sox in 2004. His acquisition allowed McCourty to shift to safety and the defense to shift into a different gear.

“No doubt he’s helped us a lot,” said McCourty. “He’s a very confident player and a very good player, and he plays that way. [Monday night] to have him out there playing very good football against one of the top receivers, not just in the NFL now, but of all time. I think he’s done a good job of just filling that role.

“I think everyone on this defense has done a good job from Day 1 of just saying, ‘We have to keep improving.’ We had some bad games where it came down to a couple of points. We said, ‘If we just keep improving we’ll be where we want to be at the end of the season.’ ”

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